What is a common indicator that a vehicle's battery may need replacement?

A common indicator that a vehicle's battery may need replacement is when the battery is over three years old and shows signs of corrosion or leaks. Batteries have a limited lifespan, typically around three to five years, and as they age, they become less effective at holding a charge. Corrosion or leaks are clear physical signs that the battery is failing. Corrosion can impede electrical flow and affect the terminals, while leaks indicate that the battery is compromised, potentially leading to performance issues or complete failure.

While the other choices might suggest battery issues, they can also stem from other problems that don’t necessarily indicate a bad battery. For instance, difficulty starting the engine could be related to issues like a faulty starter or fuel system problems. Flickering headlights when the engine is off may point to a weak electrical system or a failing alternator rather than the battery alone. Similarly, a vehicle being parked for long periods can lead to battery drain, yet it does not conclusively indicate that the battery itself needs replacement unless corroborated by additional symptoms or age. Thus, option A is a reliable and common indicator of battery replacement needs.